The invention relates to a camera system for a motor vehicle, in which incident radiation is guided to a radiation receiving unit by means of one or more deflecting mirrors, where at least one deflecting mirror is configured so as to swivel.
Modern motor vehicles employ increasingly more camera-based functions. One consideration with respect to such cameras that are used for said functions is to mount the cameras in the motor vehicle in such a manner that they are protected and require little space.
For applications in which the radiation, for example visible light or infrared radiation, is to be received from the direction of travel of the motor vehicle, conventional systems include cameras having a lens which is also oriented directly in the direction of travel. Therefore, the camera is exposed to the risk of stone impact, moisture and other environmental influences. In addition, the camera occupies a relatively large area at the front of the vehicle, a feature that may have a negative effect on the air cooling of the components of the vehicle. When it is necessary that the radiation be received from different directions, the entire camera package in such devices is designed so that it can move. In such devices an optical zoom is possible only with an optical system that is installed in the respective camera.
To increase the freedom to choose an installation site for a camera, camera systems can be used in which a single deflecting mirror or a plurality of deflecting mirrors guide the light. These mirrors serve to guide the incident radiation to the actual receiving unit of the camera system. The receiving unit can thus be shifted from the desired receiving site, where the incident radiation is to be received. The incident radiation at the receiving site is guided to the receiving unit by means of the mirror optics. The use of such a mirror optical system is appropriate especially for camera systems in which there is only limited space at the receiving site for mounting the camera system, for example in the outside mirror of a motor vehicle.
The use of an optical system with mirrors can also guarantee enhanced protection for the receiving unit of a camera system against environmental influences. Since only a deflecting mirror, and not the receiving unit itself, has to be oriented in the direction of travel, the receiving unit can be disposed in such a manner that it is protected against direct stone impact and other environmental influences. Using such a system it is also possible to produce a device having a very small frontal area, for example only causing an obstruction the size of the deflecting mirror at the front of the vehicle. Such a feature yields a number of advantages for the air cooling of the vehicle components.
It is known, for example from the DE 10255194 A1, to use swivelable deflecting mirrors for camera systems in motor vehicles, in order to cover different receiving areas. Thus, a single camera can be used for receiving radiation from different directions. Only the deflecting mirror has to be swiveled, a feature that is usually realized with less technical complexity than the swiveling of a complete camera package.
Conventional camera systems that use deflecting mirrors exhibit several drawbacks. For example, the use of rigid deflecting mirrors offers only very few options for adjusting the optical parameters of the system, such as the aperture angle for receiving the radiation. To eliminate this drawback, there exist, for example, deflecting mirrors with variable curvature and/or micro-mirror arrays. However, owing to the high cost of materials and production as well as excessive technical complexity, the practical use of such systems in automobiles has been limited.
The Exemplary embodiments of the invention provide a simple camera system for a motor vehicle, which can be mounted in such a manner that it occupies little space and is protected from the environment, and which also has a variable aperture angle.
According to the invention, a camera system for a motor vehicle is provided, in which incident radiation is guided to a radiation receiving unit by means of an optical system with one or more deflecting mirrors. At least one deflecting mirror is configured so as to swivel; and the at least one swivelable deflecting mirror exhibits a first mirror side which is suitable for deflecting incident radiation, and a second mirror side, which is also suitable for deflecting incident radiation. The second mirror side exhibits a curvature shape that is different from that of the first mirror side. The at least one swivelable deflecting mirror is swivelable in such a manner that incident radiation can selectively be guided to the receiving unit by either the first or by the second mirror side.
Other advantageous embodiments and further developments of the invention are disclosed in the following.
According to the embodiments of the invention, it is always only either the first or the second mirror side that can be selected to effectively act as the deflecting mirror. No expensive mechanism to adapt the shape of the curvature of a deflecting mirror is necessary. Instead, the mirror side acting as the effective deflecting mirror, is simply alternated between the two sides of the mirror. For example, the deflecting mirror may be rotated about 180 degrees to switch between the two reflective sides thereof.
The invention achieves with very little technical complexity the feature that the aperture angle of the camera system can be varied, at least between any two sets of characteristics. In addition to a variation of the aperture angle, any variation in the optical characteristics that can be produced by different shapes of the curvature of the two mirror sides can be achieved by switching between the two mirror sides. For example, the first mirror side may exhibit a symmetrical distortion characteristic, while the second mirror side may have an asymmetrical distortion characteristic.
Additional embodiments of the invention can also include deflecting mirrors with more than two mirror sides and correspondingly more than two different shapes of curvature. However, a swivelable deflecting mirror with two mirror sides disposed back to back, which are offset from each other by approximately 180 degrees, can be produced in a very simple way with little material. The exemplary deflecting mirror can be constructed substantially flat and with very little weight. In different embodiments, the assembly may have a configuration with six mirror sides, for example disposed in the shape of dice.
In one embodiment, the camera system includes a drive mechanism for swiveling at least one swivelable deflecting mirror and a related drive control. The low weight of the deflecting mirror is especially advantageous for dimensioning such a drive.
For example, the at least one swivelable deflecting mirror can be swiveled in such a manner that with a single mirror side radiation from different directions can be guided to the radiation receiving unit. Therefore a swivel function, to orient the effective deflecting mirror towards multiple sources of radiation, can also be used in connection with the invention. According to an especially preferred embodiment of the invention, the at least one swivelable deflecting mirror can be rotated about at least two rotational axes, in order to guide the radiation from different directions to the radiation receiving unit with a single mirror side. Thus, for example, the effective deflecting mirror can swing along both a horizontal and a vertical translation path.
The exemplary swivelable deflecting mirror can be swiveled about a rotational axis in such a manner that the source direction of the radiation, which is guided to the radiation receiving unit by the single effective mirror side, can be varied as desired. In addition, the mirror side that is used as the effective mirror side can be alternated. In this way a single drive accomplishes both a swivel function for receiving the radiation from different directions and a switching function that changes the mirror side that acts as the effective reflective surface of the deflecting mirror. A drive control to achieve these two functions can be implemented correspondingly with a simple design.
The camera system according to the embodiments can be used for a variety of vehicle functions by using different mirror sides of the deflecting mirror. Similarly, the inventive camera system can be used for various modes of a vehicle function by using the different mirror sides of the deflecting mirror. For example, the first mirror side may be constructed in such a manner that it provides a large effective aperture angle for taking a picture with the camera system. This feature may be helpful, for example, in monitoring the near environment of the vehicle. The second mirror side may be constructed in such a manner that it provides a small effective aperture angle for taking a picture with the camera system, a feature that offers many advantages in monitoring the near field over a wide range.
In another embodiment of the invention, the radiation receiving unit may be suitable for receiving infrared radiation. Specifically, the radiation receiving unit can be suitable for receiving infrared radiation of the near and/or far infrared range. The above-described benefits with respect to protection against stone impact, moisture and other environmental influences apply especially to infrared cameras, which are often very expensive. Since infrared cameras are also often relatively bulky compared to other cameras, the invention provides the additional benefit of a small size, suited to the limited space at the desired location and promoting the unimpeded air cooling of the vehicle components by covering as little frontal area as possible at the front of the vehicle.
In embodiments where the receiving unit is suitable for receiving infrared radiation, the related mirror optical system is also suitable for guiding the infrared radiation to the receiving unit. Accordingly, the surface of the first mirror side of the deflecting mirror and the surface of the second mirror side of the deflecting mirror are preferably suited for reflecting infrared radiation. This requires special materials, such as, for example, high-grade steel and germanium. Consequently, at least the surfaces of the first and the second mirror side of the deflecting mirror used for infrared applications may be made preferably of fine-grade steel and/or germanium. To use the respective material economically, the mirror sides of the deflecting mirror may be only coated with the desired material.
In an exemplary camera system according to the invention, the swivelable deflecting mirror can be housed both outside the camera package, or may be housed jointly with the radiation receiving unit inside the camera package. In the latter case, owing to the housing of the camera package, the deflecting mirror as well as its mounting and its drive can receive greater protection against environmental influences.
Other objects, advantages developments and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.